High-frequency heating apparatus

ABSTRACT

A high-frequency heating apparatus comprises a heating chamber, a high-frequency generator, a waveguide, an antenna, a motor for rotating the antenna, and a stage ( 6 ) provided above and near the antenna to partition the heating chamber and made of dielectric. A rotary base on which an object to be heated is mounted is provided on the stage. A first magnet is provided to the antenna. A second magnet is provided on the rotary base at a place corresponding to the first magnet on the rotary base. By utilizing the magnetic coupling between the first and second magnets, the rotary base is rotated in synchronism with the rotation of the antenna. While maintaining the advantages of conventional antenna high-frequency heating apparatuses, the heating efficiency by grill heating or oven heating is enhanced, and minute heating uniformness is achieved.

TECHNICAL FIELD

The present invention relates to a high-frequency heating apparatus(hereinafter also referred to as a “microwave oven”), and moreparticularly to an antenna-type high-frequency heating apparatus.

BACKGROUND ART

Roughly speaking, uniform heating inside the heating compartment of amicrowave oven is achieved by the use of a turntable, stirrer, orantenna. Now, a brief description will be given of how uniform heatingis achieved by the use of each of these. Where a turntable is used, aheating target is placed on the turntable provided on the floor of theheating compartment, and the turntable is rotated. Thus, thehigh-frequency wave radiated into the heating compartment through anopening formed on a side wall surface or the ceiling surface thereofstrikes the heating target uniformly from all directions, therebyheating it. This is the method that is currently most commonly used inmicrowave ovens. FIGS. 32 and 33 are a sectional view and a perspectiveview, respectively, of an example of a microwave oven adopting thismethod. A motor 5 is provided on the outside of the floor of the heatingcompartment 1, and the spindle 51 of this motor 5 penetrates the floorof the heating compartment 1 through a hole formed thereon so as toprotrude inward from the floor of the heating compartment 1. On thisspindle 51 protruding from the floor of the heating compartment 1, adisk-shaped turntable T is pivoted so that, as the motor 5 is driven,the turntable T rotates. On the other hand, the high-frequency waveradiated from a magnetron (high-frequency generator) 2 is guided througha waveguide 33, and is then radiated into the heating compartment 1through an opening 101 formed on the side surface of the heatingcompartment 1. Thus, the high-frequency wave strikes the heating target(not illustrated) placed on the rotating turntable T, thereby heatingit. The turntable T may instead be driven with magnetic coupling asdisclosed in, for example, Japanese Patent Application Published No.S61-13359 and Japanese Patent Applications Laid-Open Nos. S58-220387 andS59-14294.

Where a stirrer is used, typically, as shown in FIGS. 34 and 35, a metalhigh-frequency wave diffusing wheel is provided as the stirrer in thiscase, close to the heating compartment 1, inside an opening 101 formedin the ceiling surface of the heating compartment 1. This wheel isrotated with a motor 31 so that, as the high-frequency wave radiatedfrom a magnetron 2 is radiated into the heating compartment 1 throughthe opening 101, the intensity of the electromagnetic field of thehigh-frequency wave is varied by diffusion by the rotating wheel. Withthis method, uniform heating is possible with no movement in the heatingtarget. The heating target is placed on a stage T′ substantiallyrectangular in shape and made of a dielectric material (typically glass,ceramic, or the like).

Where an antenna is used, for example as shown in FIG. 36, while, on onehand, the high-frequency wave radiated from a magnetron 2 is guidedthrough a waveguide 3 to the outside of the floor of the heatingcompartment 1, the receiver portion 41 of an antenna 4 is put through anopening 11 formed on the floor of the heating compartment 1 so as toprotrude into the waveguide 3 so that, on the other hand, thehigh-frequency wave inside the waveguide 3 is propagated from thereceiver portion 41 to the radiator portion 42 of the antenna 4. Thisradiator portion 42 of the antenna 4 is rotated with a motor 5 so thatthe high-frequency wave heats the heating target uniformly (for example,as disclosed in Japanese Patent Application Laid-Open No. H11-8057). Theheating target is placed on a stage 6 that is provided above and closeto the antenna so as to partition the interior of the heatingcompartment 1 and that is made of a dielectric material (typicallyglass, ceramic, or the like). This method permits the heating target tobe placed near the radiator portion 42 of the antenna 4 from which thehigh-frequency wave is radiated, and is thus superior to the othermethods in heating efficiency. Today, this method is becomingincreasingly widespread in microwave ovens for use in convenience storesand other food processing and selling businesses.

Of these different methods for uniform heating of a heating target,whereas that using a turntable keeps the heating target rotating whileit is heated, that using a stirrer and that using an antenna keep it atrest while it is heated. From the viewpoint of uniform heating, it isgenerally believed that the methods using a turntable, an antenna, and astirrer are the best, second-best, and third-best, respectively.

From the viewpoint of the area inside the heating compartment which canbe used for the placement of the heating target, however, whereas themethod using a turntable only offers the area of the turntable itself,that using a stirrer and that using an antenna, which require nomovement in the heating target, offer the whole area of the floor of theheating compartment. Thus, the latter two permit more efficient use ofthe heating compartment, and accordingly permit more of the heatingtarget to be heated at a time, provided that the volume of the heatingcompartment is equal.

From the viewpoint of easy cleaning of the floor of the heatingcompartment, the method using a turntable with magnetic coupling andthat using a stirrer does not need through holes formed on the floor ofthe heating compartment, and thus permits comparatively easy cleaning ofthe floor of the heating compartment because this surface is largelyflat once the turntable or stage is removed. Also with the method usingan antenna, the stage provided fixedly above the antenna virtuallyserves as the floor wall of the heating compartment, and the surface ofthis stage is extremely easy to clean because it is not only flat butalso made of a dielectric material such as glass or ceramic.

In recent years, increasingly high importance has come to be placed onheating efficiency, efficient use of the interior volume of the heatingcompartment, and easy cleaning of the heating compartment. This trendhas been accompanied by revaluation of antenna-type microwave ovens forhousehold use.

Incidentally, some recently developed microwave ovens are givencomposite functions by being equipped for, as well as heating using ahigh-frequency wave, grill heating and oven heating using a heater.Grill heating is achieved by the use of a glass-tube heater or sheathheater provided on the ceiling of the heating compartment, off thecenter thereof. With this heater heated so that its surface temperatureis 600° C. or higher, the heating target is rotated so that it as awhole is roasted uniformly and quickly.

On the other hand, in a conventional antenna-type microwave oven, theheating target remains at rest on the stage, and therefore, to give themicrowave oven composite functions, for example by adding thereto acapability of grill heating, a heater H needs to be arranged over theentire ceiling surface of the heating compartment 1. Arranging theheater H over the entire ceiling surface, however, results in the heaterH occupying a large area. This lowers the temperature to which theheater H can be heated, and increases the duration for which it needs tobe heated. Disadvantageously, the heating duration cannot be shortenedwithout increasing the power consumption by the heater.

Moreover, the method using an antenna, just because it keeps the heatingtarget at rest, occasionally produces unsatisfactory results in thepreparation of, for example, egg dishes such as chawan-mushi, a Japaneseegg-based pot-steamed hotchpotch, which require delicately controlleduniform heating.

Other modern microwave ovens are equipped with stirring foodstuffs. Withthese, the entire procedure for preparing a dish, for example a steweddish such as curried stew, or for preparing dough for bread can be gonethrough continuously, from the preparation of ingredients up to theheating and finishing of the target dish. An example of this type ofmicrowave oven is shown in FIG. 38. The microwave oven shown in FIG. 38has a turntable, which can be interchanged with a container 8 having astirring wheel 83 inside it. When this container 8 is placed inside theheating compartment 1, the rotary shaft 82 of the stirring wheel 83 iscoupled with the spindle 51 of the motor 5 for rotating the turntable.As the stirring wheel 83 is rotated inside the container 8, it stirs thefoodstuffs put therein (for example, as disclosed in Japanese PatentApplications Laid-Open Nos. H10-211098 and H11-121161).

On the other hand, in a conventional antenna-type microwave oven, thereis provided no mechanism for driving a stirring wheel. This makes itimpossible to add thereto a function of automatic stirring.

DISCLOSURE OF THE INVENTION

In view of the conventionally experienced problems mentioned above, itis an object of the present invention to provide an antenna-typemicrowave oven that, while maintaining the advantages it hasconventionally had, offers enhanced heating efficiency in grill heatingand oven heating and permits delicately controlled uniform heating.

It is anther object of the present invention to provide an antenna-typemicrowave oven that is capable of automatically stirring foodstuffs putin a container placed in the heating compartment.

To achieve the above objects, according to the present invention, ahigh-frequency heating apparatus is provided with: a heating compartmentin which a heating target is heated; a high-frequency wave generatorthat generates a high-frequency wave; a waveguide through which thehigh-frequency wave generated by the high-frequency wave generator isguided to an opening formed on the heating compartment wall; a freelyrotatable antenna that feeds the high-frequency wave inside thewaveguide into the heating compartment through the opening and that hasa receiver portion and a radiator portion; a motor that rotates theantenna; and a stage that is provided above and close to the antenna soas to partition the interior of the heating compartment and that is madeof a dielectric material. In this high-frequency heating apparatus, arotary member is placed on the stage, and either magnets are provided onboth the rotary member and the antenna, or a magnet is provided on oneof the rotary member and the antenna and a magnetic material is providedon the other, so that the magnetic coupling between the antenna and therotary member is exploited to rotate the rotary member as the antennarotates.

Here, from the viewpoint of permitting rotatable placement of theheating target in an antenna-type microwave oven, enhancing the heatingefficiency in grill heating and oven heating, and permitting uniformhigh-frequency heating of the heating target, it is preferable to use,as the rotary member, a rotary stage provided with: a support memberhaving a plurality of rollers and magnets; and a table that is supportedon the support member and on which the heating target is placed.Moreover, to permit the table to rotate faster than the antenna, it ispreferable that the table be supported on the plurality of rollers bybeing kept in contact therewith so that, as the rollers rotate, thetable rotates.

From the viewpoint of mechanical strength and durability, it ispreferable that the support member be made of metal. In this case, it ispreferable that the support member have openings or cuts formed thereinthrough which to pass the high-frequency wave radiated from the antenna.

The rotary member may be a stirring member provided in a containerplaced on the stage. This, while maintaining the advantage of anantenna-type microwave oven that the floor of the heating compartmenthas a flat surface without holes and is thus easy to clean, makes itpossible to stir with the stirring member the foodstuffs put in thecontainer placed in the heating compartment.

To permit smooth rotation of the stirring member inside the container,and to achieve effective stirring of the heating target, it ispreferable that the stirring member be provided with: a disk-shapedbase; a stirring wheel that is formed on the base; and two or morerollers pivoted in a peripheral portion of the base.

From the viewpoint of preventing surface contact between the radiatorportion of the antenna and the bottom surface of the stage and therebyachieving smooth rotation without friction thereof, and in additionprecisely controlling the distance between the radiator portion of theantenna and the bottom surface of the stage and the length over whichthe receiver portion of the antenna protrude into the waveguide, it ispreferable to provide a restricting member on at least one of theantenna and the stage in order to restrict the movement of the antennain the axial direction. Preferably, the antenna is composed of acylindrical receiver portion and a substantially disk-shaped radiatorportion fitted at the top end of the receiver portion coaxiallytherewith, and the restricting member is formed on the top surface ofthe radiator portion of the antenna at equal angular intervals in thecircumferential direction.

From the viewpoint of preventing magnetic attraction between the magnetfitted on the antenna and the floor, made of a magnetic material, of theheating compartment and thereby achieving smooth rotation of theantenna, it is preferable that the side of the magnet fitted on theantenna which faces the stage be covered with a nonmagnetic member, andthat the side of the same magnet which faces the floor of the heatingcompartment be covered with a magnetic member. Here, when the antenna isformed of a nonmagnetic member, it is preferable that the magnet beprovided on the bottom surface of the antenna, and that the surface ofthe magnet be covered with a magnetic member. By contrast, when theantenna is formed of a magnetic member, it is preferable that the magnetbe provided on the top surface of the antenna, and that the surface ofthe magnet be covered with a nonmagnetic member.

For the purpose of browning the heating target and for other purposes, aheater is sometimes brought close to the periphery of the antenna andoperated with the antenna stationary. In this case, the magnet fitted onthe antenna is locally exposed to high temperature. In general, a magnetundergoes irreversible demagnetization at high temperature. Thus, themagnet, if demagnetized at high temperature, will weaken the magneticcoupling between the antenna and the rotary member, leading to loss ofrotation of the rotary member. To avoid this, it is strongly recommendedto rotate the antenna when the heater is operating in order to reducethe effect of the heat generated by the heater on the magnet fitted tothe antenna.

It is preferable to keep the antenna rotating even after the heaterstops being heated until a predetermined length of time elapses or untilthe temperature falls below a predetermined temperature. To permit theuser to safely take out the heating target placed on the rotary member,it is preferable to provide a detector for detecting whether the door ofthe heating compartment is open or closed so that, when the door isopened after the heater stops being heated, the rotation of the antennais stopped. On the other hand, when the rotary member is not used andthe heating target is placed directly on the stage, even if the door isopened while the antenna is rotating after the heater stops beingheated, the rotation of the antenna need not be stopped.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an exterior view showing an example of a microwave ovenaccording to the invention.

FIG. 2 is a front sectional view of the microwave oven of FIG. 1.

FIG. 3 is a side sectional view of the microwave oven of FIG. 1.

FIG. 4 is a diagram showing how high-frequency heating is performed withthe heating target placed on the stage

FIG. 5 is a diagram showing how the antenna and the table rotate at thesame speed.

FIG. 6 is a perspective view showing an example of the antenna.

FIG. 7 is a diagram showing how the antenna and the table rotate atdifferent speeds.

FIG. 8 is a perspective view showing an example of the support member.

FIG. 9 is a perspective view showing another example of the supportmember.

FIG. 10 is a front sectional view showing another embodiment of amicrowave oven according to the invention.

FIG. 11 is a front sectional view showing another example of a microwaveoven according to the invention.

FIG. 12 is a front sectional view of a microwave oven, when the rotarymember is not used.

FIG. 13 is a perspective view showing an example of the antenna.

FIG. 14 is a perspective view showing another example of the antenna.

FIG. 15 is a partial sectional view, when the antenna of FIG. 12 isarranged in the microwave oven.

FIG. 16 is a partial sectional view, when the rotary stage is arrangedin the apparatus of FIG. 13.

FIG. 17 is a front sectional view showing another example of a microwaveoven according to the invention.

FIG. 18 is a partial sectional view of the microwave oven of FIG. 15.

FIG. 19 is a partial sectional view showing another implementation of amicrowave oven according to the invention.

FIG. 20 is a partial sectional view showing another implementation of amicrowave oven according to the invention.

FIG. 21 is a partial sectional view showing another implementation of amicrowave oven according to the invention.

FIG. 22 is a vertical sectional view, when the rotary member is used ina microwave oven provided with a lower heater.

FIG. 23 is a vertical sectional view, when the rotary member is not usedin a microwave oven provided with a lower heater.

FIG. 24 is a horizontal sectional view of the microwave oven of FIG. 22.

FIG. 25 is a diagram showing an example of the temperature variationcharacteristics of the magnets provided on the antenna in a microwaveoven according to the invention.

FIG. 26 is a control block diagram in a microwave oven according to theinvention.

FIG. 27 is a flow chart during heating as used by the control blockaccording to the invention.

FIG. 28 is a flow chart after heating as used, in a first embodiment, bythe control block according to the invention.

FIG. 29 is a flow chart after heating as used, in a second embodiment,by the control block according to the invention.

FIG. 30 is a flow chart after heating as used, in a third embodiment, bythe control block according to the invention.

FIG. 31 is a diagram showing an example of the relationship between thespecified heating duration and the duration for which the rotary antennais stopped as used by the control block according to the invention.

FIG. 32 is a front sectional view showing a conventional turntable-typehigh-frequency heating apparatus.

FIG. 33 is a perspective view showing a conventional turntable-typehigh-frequency heating apparatus.

FIG. 34 is a front sectional view showing a conventional stirrer-typehigh-frequency heating apparatus.

FIG. 35 is a perspective view showing a conventional stirrer-typehigh-frequency heating apparatus.

FIG. 36 is a side sectional view showing a conventional antenna-typehigh-frequency heating apparatus.

FIG. 37 is a front sectional view showing a conventional high-frequencyheating apparatus provided with a stirring function.

FIG. 38 is a side sectional view showing a conventional antenna-typehigh-frequency heating apparatus provided with a heater.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, high-frequency heating apparatuses (microwave ovens)according to the present invention will be described with reference tothe accompanying drawings. It should be understood that theseembodiments are not meant to limit the invention in any way.

FIG. 1 is an exterior perspective view showing an example of a microwaveoven according to the invention. FIGS. 2 and 3 are respectively a frontsectional view and a side sectional view thereof. According to theinvention, a microwave oven is provided with a heating compartment 1made of metal and having a substantially rectangular shape, and awaveguide 3 provided on the outside of the floor of the heatingcompartment 1 so as to be adjacent thereto. At one end of the waveguide3, a magnetron (high-frequency wave generator) 2 is fitted, and, at theother end of the waveguide 3, an opening 11 that leads to the heatingcompartment 1 is formed. On the floor portion of the heating compartment1, an antenna 4 is provided. The antenna 4 is composed of a cylindricalreceiver portion 41 and a disk-shaped radiator portion 42 fitted at thetop end of the receiver portion 41. On the top surface of the radiatorportion 42, first magnets 43 are arranged at equal angular intervals inthe circumferential direction, and a protective member 44 is fitted soas to cover the first magnets 43.

The cylindrical receiver portion 41 is put through the opening 11 formedon the floor of the heating compartment 1 so as to protrude into thewaveguide 3, and is connected, at the bottom end thereof, to the spindleof a motor 5 provided on the outside of the floor of the waveguide.Thus, as the motor 5 is driven, the antenna 4 rotates.

Inside the heating compartment 1, above and close to the antenna 4, astage 6 is fitted so as to partition the interior of the heatingcompartment 1. This stage 6 is made of a dielectric material such asglass or ceramic so as to transmit high-frequency waves. As will bedescribed later, when a heating target is heated by high-frequencyheating alone, the heating target S is placed directly on the stage 6.Made of glass, ceramic, or the like, the stage 6 has a smoother surfacethan a metal member, and is thus far easier to clean.

On the top surface of the stage 6, a rotary stage (rotary member) 7having a heating target S placed thereon is placed. The rotary stage 7has a disk-shaped support member 71 and a table 72 supported on the topsurface of the support member 71. On the peripheral wall of the supportmember 71, a plurality of rollers 75 are pivoted on shafts 76. On thebottom surface of the support member 71, second magnets 73 are fitted inpositions corresponding to the first magnets 43, and a protective member74 is fitted so as to cover them. Thus, as the antenna 4 rotates, thanksto the magnetic coupling between the first magnets 43 and the secondmagnets 73, the support member 71 rotates together, with the result thatthe table 72 supported on the support member 71 also rotates. Here, themagnetic coupling can be obtained even when either the first magnets 43or the second magnets 73 are replaced with pieces of a magneticmaterial. On the ceiling of the heating compartment 1, off the centerthereof, a heater H used for grill heating is fitted.

In the microwave oven constructed as described above, the high-frequencywave generated by the magnetron 2 is guided through the waveguide 3 tothe receiver portion 41 of the antenna 4. The high-frequency wave isthen propagated from the receiver portion 41 to the radiator portion 42,and is then radiated into the heating compartment 1. Here, the radiatorportion 42 is rotated by the motor 5, and this permits thehigh-frequency wave to be radiated uniformly into the heatingcompartment. FIG. 6 is a perspective view showing an example of theantenna. In the antenna shown in this figure, the high-frequency wave isradiated mainly from the edges of openings 45 and 46 formed in theradiator portion 42. Needless to say, the antenna 4 may be given anyother shape than specifically shown here: it may be in the shape of, forexample, a bar or an elongate plate.

The high-frequency wave radiated from the radiator portion 42 of theantenna 4 is transmitted through the stage 6, and then strikes, directlyor after being reflected off the inner walls of the heating compartment,the heating target S, thereby heating it. Here, when the heating targetS is heated with the high-frequency wave alone, as shown in FIG. 4, therotary stage 7 is removed from the heating compartment 1, andhigh-frequency heating is performed with the heating target S placed onthe stage 6. In this way, the advantages that an antenna-typeconstruction has conventionally had are maintained. Specifically, asdescribed earlier, the antenna 4 rotates right below the stage 6 onwhich the heating target S is placed, and thus the antenna 4 permits thehigh-frequency wave to strike the heating target S uniformly, therebyheating it uniformly. Moreover, in this case, the entire space insidethe heating compartment 1 can be efficiently used.

On the other hand, when grill heating is performed, as shown in FIG. 2,the rotary stage 7 is placed on the stage 6, and the heating target S isplaced on the table 72 of the rotary stage 7. When, as the motor 5 isdriven, the antenna 4 rotates, thanks to the magnetic coupling betweenthe first magnets 43 and the second magnets 73, the support member 71along with the table 72 rotates together. Since, as shown in FIG. 3, theheater H for grill heating is arranged in a position slightly deviatedrightward from the center of the heating compartment 1, by rotating theheating target 1, it as a whole can be heated uniformly with the heaterH. In grill heating, rotating the table 72 and the antenna 4 at the samespeed does not affect the heating performance, and therefore, as shownin FIG. 5, the table 72 is supported on the support member 71 in such away that the bottom surface of the table 72 does not make contact withthe rollers 75 of the support member 71.

When high-frequency heating and grill heating are performed together, asin combined grill heating, the heating target S is placed on the table72 of the rotary stage 7, and the magnetic coupling between the firstmagnets 43 and the second magnets 73 is exploited so that, as theantenna 4 rotates, the rotary stage 7 rotates together. In this case,however, the antenna 4 and the table 72, on which the heating target Sis placed, need to be rotated at different speeds. This is because, ifthe antenna 4 and the table 72 are rotated at the same speed, thehigh-frequency wave radiated from the antenna 4 strikes only aparticular part of the heating target S. The antenna 4 and the table 72can be rotated at different speeds, for example, in the followingmanner. As shown in FIG. 7, the bottom surface of the table 72 is keptin contact with the rollers 75 fitted on the peripheral wall of thesupport member 71 so that the rollers 75 supports the table 72 andsimultaneously permits it to rotate. With this construction, while thesupport member 71 rotates at the same speed as the antenna 4, the table72 supported on the rollers 75 of the support member 71 rotates at twicethe rotation speed of the antenna 4. Thus, the heating target S on thetable 72 is as a whole heated uniformly. Likewise, also in a case wherehigh-frequency heating alone is used and the rotary stage 7 is used, theantenna 4 and the table 72 are rotated at different speeds.

Considering the heat resistance and the mechanical strength requiredduring heating using the heater, it is preferable that the supportmember 71 used in the invention be made of a metal. In this case,however, since a metal material does not transmit high-frequency waves,it is preferable that the support member 71 have, for example, openings77 formed therein through which to permit the passage of thehigh-frequency wave as shown in FIG. 8, or parts thereof cut outelsewhere than in the structurally necessary part thereof to leave openspaces as shown in FIG. 9.

On the other hand, for high-frequency heating, the table 72 used in thisinvention may be made of any material so long as it does not stop highfrequency waves. From the viewpoint of mechanical strength and easinessof cleaning, it is recommended that the table 72 be made of glass,ceramic, or the like. In contrast, for grill heating and convectionheating, it is preferable to use a table made of a nonmagnetic metal.

Next, another example of a microwave oven according to the inventionwill be described. An outstanding feature of this microwave oven is thatmagnetic coupling is exploited to permit a stirring member (rotarymember) arranged inside a container to rotate as an antenna rotates.FIG. 10 is a front sectional view showing an example of a microwave ovenaccording to this invention. It should be noted that, in the followingdescription, no explanations will be repeated of such components andstructures as are found also in the microwave oven of FIG. 1, andchiefly differences therefrom will be discussed.

On the stage 6, a stirring container (rotary member) 8 made of adielectric material is mounted, and, inside this stirring container 8, astirring member 9 is arranged. The stirring member 9 is provided with adisk-shaped base 91, a stirring wheel 92 arranged upright on the topsurface of the base, and rollers 95 pivoted in a peripheral portion ofthe base 91. At the center of the base 91, a through hole 96 is formed,and though this through hole 96, a projection 81 formed at the center ofthe floor of the stirring container 8 is inserted. Thus, the stirringmember 9 is fitted inside the stirring container 8 so as to be rotatableabout the projection 81. Moreover, on the bottom surface of the base 91,in positions corresponding to the first magnets 43 arranged on the topsurface of the antenna 4, second magnets 93 are fitted.

With the microwave oven constructed as described above, a heating targetcan be heated while it is stirred in the following manner. First theheating target (not illustrated) is put in the stirring container 8, andthen the motor 5 is driven to rotate the antenna 4. Now, thanks to themagnetic coupling between the first magnets 43 and the second magnets93, as the antenna 4 rotates, the stirring member 9 inside the stirringcontainer 8 rotates together. Thus, the stirring wheel 92 of thestirring member 9 stirs the heating target. In this way, the heatingtarget put in the stirring container 8 is heated by the high-frequencywave and is simultaneously stirred by the stirring member 9. With thismicrowave oven, the entire procedure for preparing a dish, for example astewed dish such as curried stew, or for preparing dough for bread canbe gone through continuously, from the preparation of ingredients up tothe heating and finishing of the target dish.

Moreover, since the projection 81 formed at the center of the base ofthe stirring container 8 is inserted into the through hole 96 formed inthe stirring member 9 so that the stirring member 9 is rotated about theprojection 81, even when the stirring wheel 92 receives a strongresistance from the heating target, the center of the stirring member 9does not become misaligned, nor do the first magnets 43 and the secondmagnets 93 become magnetically decoupled. This permits stable stirring.

FIG. 11 shows another example of a microwave oven according to theinvention. An outstanding feature of the microwave oven shown in FIG. 11is that restricting members 47 for restricting the movement of theantenna 4 in the axial direction are provided on the top surface of theradiator portion 42. This prevents the magnetic coupling from causingthe antenna 4 to move upward in the axial direction and make surfacecontact with the bottom surface of the stage 6. Moreover, restrictingthe movement of the antenna in the axial direction permits stableradiation of the high-frequency wave from the antenna. It should benoted that, in the following description, no explanations will berepeated of such components and structures as are found also in themicrowave oven of FIG. 1, and chiefly differences therefrom will bediscussed.

In the microwave oven of FIG. 11, projections (restricting members) 47are provided on the top surface of the radiator portion 42 of theantenna 4 at equal angular intervals in the circumferential direction.With the rotary stage 7 placed on the stage 6, the magnetic attractionbetween the first magnets 43 and the second magnets 73 causes theantenna 4 to move upward, but the projections 47 formed on the topsurface of the radiator portion 42 of the antenna 4 makes contact withthe bottom surface of the stage 6, thereby preventing the radiatorportion 42 from making surface contact with the stage 6.

When the heating target S is heated with the high-frequency wave alone,as shown in FIG. 12, the rotary stage 7 may be removed from the heatingcompartment 1 and high-frequency heating is performed with the heatingtarget S placed directly on the stage 6. In this way, the advantagesthat an antenna-type construction has conventionally had are maintained.Specifically, as described earlier, the antenna 4 rotates right belowthe stage 6 on which the heating target S is placed, and thus theantenna 4 permits the high-frequency wave to strike the heating target Suniformly, thereby heating it uniformly. Moreover, in this case, thespace inside the heating compartment 1 can be efficiently used. In thiscase, no magnetic attraction is working, and therefore the antenna 4,with its own weight, moves downward, with the projections 47 kept out ofcontact with the stage 6.

On the other hand, when grill heating or oven heating is performed,rotating the table 72 and the antenna 4 at the same speed does notaffect the heating performance, and therefore the table 72 may besupported on the support member 71 in such a way that the bottom surfaceof the table 72 does not make contact with the rollers 75 of the supportmember 71.

FIG. 13 is a perspective view of the antenna used in the microwave ovenof FIG. 11. In this antenna, the high-frequency wave is radiated mainlyfrom the edges of openings 45 and 46 formed in the radiator portion 42.Needless to say, the antenna 4 may be given any other shape thanspecifically shown here: it may be in the shape of, for example, a baror an elongate plate.

FIG. 14 shows another example of the antenna. In this antenna, used asthe restricting members are rollers 48 that are pivoted at the peripheryof the disk-shaped radiator portion 42. Specifically, the rollers 48 arefitted to the radiator portion 42 in such a way that the top ends of therollers 48 come above the top surfaces of the radiator portion 42 andthe protective member 44. FIG. 15 is a partial sectional view when thisantenna is placed in the microwave oven. As will be clear from thisfigure, when the rotary stage 7 is not placed on the stage 6, there isleft a gap d between the top ends of the rollers 48 and the stage 6,whereas the bottom ends of the rollers 48 are in contact with the floorof the heating compartment 1. When the microwave oven is used in thisstate, for example, by performing high-frequency heating alone, as themotor 5 is driven, the antenna 4 rotates, and thus the rollers 48 rollon the floor of the heating compartment 1. This keeps the radiatorportion 42 and the floor of the heating compartment 1 parallel. Needlessto say, the rollers 48 may instead be kept out of contact with the floorof the heating compartment 1.

FIG. 16 shows a partial sectional view when the rotary stage 7 is placedon the stage 6. In this case, the magnetic attraction between the firstmagnets 43 and the second magnets 73 causes the antenna 4 to move upwardin the axial direction, but the top ends of the rollers 48 pivoted atthe periphery of the radiator portion 42 make contact with the bottomsurface of the stage 6, thereby restricting the movement. Here, it ispreferable that the movement distance of the antenna 4 in the axialdirection be 5 mm or less. If the movement distance of the antenna 4 ismore than 5 mm, the distance between the radiator portion 42 of theantenna 4 and the floor of the heating compartment 1 and the length overwhich the receiver portion 41 protrudes into the waveguide 3 vary toogreatly, possibly leading to unstable radiation of the high-frequencywave. It is further preferable that the movement distance be 1 mm orless. In practice, the movement distance of the antenna can be adjustedby adjusting the gap d, shown in FIG. 15, between the top ends of therollers 48 and the bottom surface of the first stage 6.

When the microwave oven is used in this state, for example, byperforming high-frequency heating and grill heating simultaneously, asthe motor 5 is driven, the antenna 4 rotates, and thus the rollers 48roll on the bottom surface of the stage 6. This prevents the peripheralportion of the radiator portion 42 from being bent upward in the axialdirection by the magnetic attraction, and thus keeps the radiatorportion 42 and the stage 6 parallel.

As still another example of a microwave oven according to the invention,the following construction is possible. In a case where the heatingcompartment 1 is made of a magnetic material, to allow the antenna 4 torotate smoothly, no magnetic attraction needs to be permitted to appearbetween the first magnets 43 and the floor of the heating compartment 1;simultaneously, to allow the rotary stage 7 to rotate smoothly as theantenna 4 rotates, the magnetic attraction between the first magnets 43and the second magnets 73 needs to be maintained. This is achieved bycovering the side of the first magnets 43 facing the stage with anonmagnetic member, and covering the side of the first magnets 43 facingthe floor of the heating compartment 1 with a magnetic member. FIGS. 17and 18 are respectively a front sectional view and a partial sectionalview showing an example of such a microwave oven. It should be notedthat, in the following description, no explanations will be repeated ofsuch components and structures as are found also in the microwave ovenof FIG. 1, and chiefly differences therefrom will be discussed.

In the microwave oven of FIG. 17, what is located adjacently above thefirst magnets 43 fitted on the bottom surface of the radiator portion 42a is the radiator portion 42 a of the antenna, which is made of alumina(a nonmagnetic material). This ensures magnetic coupling between thefirst magnets 43 and the second magnets 73. On the other hand, the firstmagnets 43 are covered with a magnetic member 413 from below. Thispermits no magnetic attraction to appear between the floor of theheating compartment 1, which is made of a magnetic material, and thefirst magnets 43, allowing the radiator portion 42 a of the antenna 4 torotate smoothly. Accordingly, as the antenna 4 rotates, the rotary stage7 rotates at the same speed as the antenna 4, and the table 72 supportedon the rollers 75 rotates at twice the rotation speed of the antenna 4.Thus, the heating target S placed on the table 72 is heated uniformlywith the high-frequency wave radiated from the radiator portion 42 a andwith the heat from the heater H.

Here, by forming the radiator portion 42 a, which is a non-magneticmember, and the magnetic member 413 both as metal members, it ispossible to reduce the effect of the high-frequency wave on the firstmagnets 43.

FIG. 19 shows another example of the antenna 4. In the antenna 4 of FIG.19, in the bottom surface of the radiator portion 42 b, depressions 415of which the depth is greater than the thickness of the first magnets 43are formed at equal angular intervals in the circumferential direction,and the first magnets 43 are fitted there. The openings of thedepressions 415 are closed with magnetic members 414 to form flatplates. With this construction, when the first magnets 43 are fitted,they can be easily positioned; moreover, the magnetic members 414 can beeasily formed; and, moreover, the apparatus can be made thin.

FIG. 20 is a partial sectional view showing another example of amicrowave oven according to the invention. In the microwave oven of FIG.20, on the top surface of the radiator portion 42 c, which is made of amagnetic material, the first magnets 43 are fitted at equal angularintervals in the circumferential direction, and their surfaces arecovered with nonmagnetic members 416. With this construction, as withthe previously described construction, no magnetic attraction appearsbetween the floor of the heating compartment 1 and the first magnets 43,permitting the radiator portion 42 c of the antenna 4 to rotatesmoothly. On the other hand, what are located adjacently above the firstmagnets 43 are the nonmagnetic members 416, ensuring magnetic couplingbetween the first magnets 43 and the second magnets 73.

FIG. 21 shows another example of the antenna 4. In the antenna 4 of FIG.21, in the top surface of the radiator portion 42 d, depressions 418 ofwhich the depth is greater than the thickness of the first magnets 43are formed at equal angular intervals in the circumferential direction,and the first magnets 43 are fitted there. The openings of thedepressions 418 are closed with nonmagnetic members 417 to form flatplates. With this construction, as with the previously describedconstruction, when the first magnets 43 are fitted, they can be easilypositioned; moreover, the nonmagnetic members 417 can be easily formed;and, moreover, the apparatus can be made short.

Another example of a microwave oven according to the invention will bedescribed below. FIG. 22 is a vertical sectional view thereof as seenfrom the front, and FIG. 23 is a vertical sectional view thereof as seenfrom the front when the rotary stage is not used. An outstanding featureof this microwave oven is that a lower heater h built with a sheathheater as shown in FIG. 24 is arranged around the periphery of theantenna 4. This makes it possible to add a grill heating function or thelike. It should be noted that, in the following description, noexplanations will be repeated of such components and structures as arefound also in the microwave oven of FIG. 1, and chiefly differencestherefrom will be discussed.

When high-frequency heating is performed by using the antenna asordinarily performed, as shown in FIG. 23, the rotary stage 7 isremoved, and high-frequency heating is performed with the heating targetS placed directly on the stage 6. In this way, the space inside theheating compartment 1 can be efficiently used, and the advantages thatthe antenna-feed-type construction has conventionally had aremaintained.

When the heating target S needs to be rotated, as shown in FIG. 22, theheating target S is placed on the substantially circular table 72 of therotary stage 7. The rotation of the antenna 4 is transmitted to therotary stage 7 by the magnetic coupling between the first magnets 43 andthe second magnets 73 described above, making the rotary stage 7 rotate.

When the heating target S needs to be browned, it is heated with thelower heater h operated. In this case, to prevent the first magnets 43fitted to the antenna 4 from being intensively heated by the lowerheater h, the antenna 4 is rotated. Accordingly, thanks to the magneticcoupling between the first magnets 43 and the second magnets 73, therotary stage 7 rotates together.

Now, why the antenna 4 is rotated when the lower heater h is operated soas to prevent the first magnets 43 from being intensively heated will bedescribed with reference to FIG. 25. FIG. 25 shows the time-relatedtemperature variation characteristics of the individual magnets asobserved when the lower heater h is operated with or without the antenna4 rotated. Here, the stop position is arbitrary, and therefore theplotted characteristics should be understood to be a mere example.

When the lower heater h is operated with the antenna 4 stopped, thetemperature of the first magnets 43 a, 43 b, and 43 c rises as they areheated by the lower heater h. Since the magnet 43 a is the closest tothe lower heater h, its temperature rises at a higher rate than that ofthe magnets 43 b and 43 c. In general, magnets undergo irreversibledemagnetization at high temperatures. Thus, it is important to limit therise in the temperature of the magnets. For this reason, in order toprevent magnets from being overheated because of local heatconcentration at particular locations, the antennae 4 in this embodimentis rotated continuously when lower heater h is in operation. In thisway, it is possible to level out the rises in the temperature of aplurality of magnets.

FIG. 26 shows an example of the drive circuit of the microwave oven ofthis embodiment. This drive circuit is so configured as to operate, forhigh-frequency heating, the magnetron 2 and the antenna 4 and, forheater heating, operate the upper and lower heaters H and h and theantenna 4 while keeping the magnetron 2 out of operation.

As shown in FIG. 26, to the output line L1 of a plug 28 for receivingcommercially distributed alternating-current power, there are seriallyconnected the following components in the order mentioned: the firstrelay switch SW1 that is opened and closed by a safety switch 26 and thefirst relay 31; the primary coil 29 of a high-frequency drive powersupply transformer T; and the seventh relay switch SW7 that is openedand closed by the seventh relay 37. Parallel with the primary coil 29 ofthe transformer T and the seventh relay switch SW7, there are connectedseveral relay switches along with the loads driven by those relayswitches.

Specifically, these pairs of relays and loads include: the second relayswitch SW2 that is opened and closed by the second relay 32, along withthe upper heater H; the third relay switch SW3 that is opened and closedby the third relay 33, along with the lower heater h; the fourth relayswitch SW4 that is opened and closed by the fourth relay 34, along withthe antenna motor 5 for driving the antenna 4; the fifth relay switchSW5 that is opened and closed by the fifth relay 35, along with a fanmotor 39 for cooling the high-frequency drive power supply 21; and thesixth relay switch SW6 that is opened and closed by the sixth relay 36,along with an oven lamp 20 for illuminating the interior of the heatingcompartment.

The first to seventh relays 31 to 37 are driven and controlled by acontroller 27, but the control lines from the controller to each relayare not shown here. The controller 27 is connected also to a door switch22 and an oven thermistor 23 so as to receive information also from thedoor switch 22 and the oven thermistor 23.

The controller 27 is connected also to a display section 25 and to a keyoperation section 30 so as to control the display section 25 and toreceive information from the key operation section 30, respectively.Reference numeral 24 represents a magnetron.

Next, the operation will be described. First, from the key operationsection 30, information on the type of heating, i.e. whether to performhigh-frequency heating or heater heating using the upper and lowerheaters is entered, and conditions such as the heating duration arespecified. Then, a command is entered to start heating. Forhigh-frequency heating, the first, fourth, fifth, sixth, and seventhrelay switches SW1, SW4, SW5, SW6, and SW7 are turned on. As the resultof the first and seventh relay switches SW1 and SW7 being turned on, acurrent flows through the primary coil 29 of the high-frequency drivepower supply transformer T, and the high-frequency drive power supply 21starts operating. This turns the magnetron 24 on, causing it to generatea high-frequency electromagnetic wave. As the result of the fourth relayswitch SW4 being turned on, the motor 5 starts operating, causing theantenna 4 to rotate. As the result of the fifth and sixth relay switchesSW5 and SW6 being turned on, the fan motor 39 for cooling thehigh-frequency drive power supply 21 starts operating, and the oven lamp20 for illuminating the interior of the heating compartment is lit. Inthis case, the second and third relay switches SW2 and SW3 are kept off,and thus the upper and lower heaters H and h are kept out of operation.

On the other hand, for heater heating, in addition to the first, fourth,and sixth relay switches SW1, SW4, and SW6, the second and third relayswitches SW2 and SW3 are turned on so that heating is performed with theupper and lower heaters H and h. In this case, the fourth relay switchSW4 is on, in order to rotate the antenna 4.

Thus, as described earlier, the first magnets 43 fitted on the antenna 4are not locally overheated by the lower heater h. This preventsdemagnetization of the first magnets 43. Here, the seventh relay switchSW7 is kept off so that no current flows through the primary coil 29 ofthe high-frequency drive transformer T. Thus, the high-frequency drivepower supply 21 is kept out of operation, keeping the magnetron 24 outof operation.

Next, the control flow of operations performed by the controller 27 willbe described with reference to the flow charts shown in FIGS. 27 to 30.First, the flow of operations for heating will be described withreference to FIG. 27. As shown in FIG. 27, first, in step S010,according to the information entered via the key operation section 30,the controller 27 sets, as heating means, either heater heating orhigh-frequency heating. Next, in step S020, the heating duration T0 isset. Thereafter, in step S030, heating is started. When heating isstarted here, in step S040, a heating timer is reset. This heating timeris included in the controller 27. Next, in step S050, the first relayswitch SW1 is turned on so that the individual loads are connected tothe output line L1 of the plug 28 for receiving commercially distributedalternating-current power, the fourth relay switch SW4 is turned on torotate the antenna 4, and the sixth relay switch SW6 is turned on tolight the oven lamp 20 for illuminating the interior of the heatingcompartment. Next, in step 060, whether or not the heating means thatwas set in step S010 is high-frequency heating is checked. Ifhigh-frequency heating is found to have been set, then, in step S071,the fifth relay switch SW5 is turned on to drive the fan motor 39 forcooling the high-frequency drive power supply 21, and the relay switchSW7 is turned on to pass a current through the primary coil 29 of thehigh-frequency drive transformer T to operate the high-frequency drivepower supply 21 and make it generate a high-frequency electromagneticwave. If high-frequency heating is found not to have been set, then, instep S072, the second and third relay switches SW2 and SW3 are turned onto drive the upper and lower heaters H and h.

Next, in step S080, the heating timer is started to count time, andthen, in step S090, whether or not its count TC has reached thepredetermined value T0 that was set in step S020 is checked. If TC hasreached the set value, the flow returns to step S080; if TC has notreached the set value, the flow proceeds to step S100, where the first,second, third, fifth, sixth, and seventh relay switches SW1, SW2, SW3,SW5, SW6, and SW7 are turned off so that the loads other than theantenna 4 are stopped to end the heating. Next, in step S105, whether ornot the heating means is high-frequency heating is checked so that, ifit is found to be high-frequency heating, then, in step S106, the fourthrelay switch SW4 is turned off to stop the rotation of the antenna 4,finishing the flow of operations for heating.

Different embodiments are possible for the flow control after theheating means is found not to be high-frequency heating in step S105. Inone embodiment, as shown in the flow chart of FIG. 28, the rotation ofthe antenna 4 after heating is controlled by the use of a timer. Inanother embodiment, as shown in the flow chart of FIG. 29, the rotationof the antenna 4 after heating is controlled by the use of a temperaturedetector. In still another embodiment, as shown in the flow chart ofFIG. 30, the rotation of the antenna 4 after heating is controlled bythe use of a timer, and in addition the rotation of the antenna 4 iscontrolled differently between when the rotary stage 7 is used (i.e.when the heating target S is heated with the heating target S placed onthe table 72 on the rotary stage 7 that is rotated by the magneticcoupling between the first magnets 43 arranged on the antenna 4 and thesecond magnets 73 arranged on the rotary stage 7) and when the rotarystage 7 is not used (i.e. when the heating target S is heated with theheating target S placed directly on the stage 6). Now, each of theseembodiments will be described one by one with reference to the flowcharts of FIGS. 28, 29, and 30.

First, the first embodiment will be described with reference to FIG. 28.If, in step S105 in FIG. 27, the heating means is found not to behigh-frequency heating (i.e., if it is found to be heater heating), thenthe flow proceeds to step S110 in FIG. 28. In this step, the antennastop time T1, which has thus far been rotating, is set. Next, in stepS120, a stop timer is reset, and then, in step S130, the stop timer isstarted to count time. The antenna stop time T1 may be a fixed durationthat is determined in advance, or may be a function of the set heatingduration T0 or of the actual heating duration and the actual operationduration of the lower heater. By setting the antenna stop time T1 to bea function of the set heating duration T0 or the like, it is possible,when the set heating duration T0 is short, to shorten the antenna stoptime T1 accordingly. This helps eliminate unnecessary power consumption.FIG. 31 shows an example where the stop time T1 is set to be a functionof the set heating duration T0.

Next, in step S140, whether or not the door is open is checked. If thedoor is found to be open, then, irrespective of whether or not the timerhas counted to the end, in step S150, the fourth relay switch SW4 isturned off to stop the rotation of the antenna 4. Then, the flow returnsto step S140, where whether or not the door 15 is open is checked again.So long as the door 15 is found to be open, the operations in steps S140and S150 are repeated. Thereafter, when the door 15 is found not to beopen, the flow proceeds to step S160, where the fourth relay switch SW4is turned on to rotate the antenna 4.

Next, in step S170, whether or not the count of the stop timer hasreached the predetermined value T1 that was set in step S110 describedabove is checked. If the count is found to have reached thepredetermined value T1, then the flow proceeds to step S180, where thefourth relay switch SW4 is turned off to stop the rotation of theantenna 4, finishing the flow after heating. If the count is found notto have reached that value, the flow returns to step S130 to repeat theoperations in steps S130 to S170.

Next, the second embodiment will be described with reference to FIG. 29.If, in step S105 in FIG. 27 described earlier, the heating means isfound not to be high-frequency heating (i.e., if it is found to beheater heating), then the flow proceeds to step S210 in FIG. 29. In thisstep, the antenna stop temperature S1 is set. Next, in step S220, theheating compartment temperature TS is sensed, and then the flow proceedsto step S230. In this step, whether or not the door is open is checked.If the door is found to be open, then, in step S240, the fourth relayswitch SW4 is turned off to stop the rotation of the antenna 4. Then,the flow returns to step S230, where whether or not the door is open ischecked again. So long as the door is found to be open, the operationsin steps S230 and S240 are repeated. Thereafter, when the door 15 isfound not to be open, the flow proceeds to step S250, where the fourthrelay switch SW4 is turned on to rotate the antenna 4.

Next, in step S260, whether or not the heating compartment temperatureTS is equal to or lower than the predetermined value S1 that was set instep S210 described above is checked. If the temperature TS is lowerthan the predetermined value S1, then the flow proceeds to step S270,where the fourth relay switch SW4 is turned off to stop the rotation ofthe antenna 4, finishing the flow after heating. If the temperature TShas not reached the predetermined value S1, the flow returns to stepS220 to repeat the operations in steps S220 through S260.

Lastly, the third embodiment will be described with reference to FIG.30. If, in step S105 in FIG. 27 described earlier, the heating means isfound not to be high-frequency heating (i.e., if it is found to beheater heating), then the flow proceeds to step S310 in FIG. 30. In thisstep, the antenna stop time T1 is set. Next, in step S320, the stoptimer is reset, and then the flow proceeds to step S330, where the stoptimer is started to count time. Next, in step S340, whether or not thedoor is open is checked. If the door is found to be open, then, in stepS341, whether or not the rotary stage 7 is being used is checked. If therotary stage 7 is found to be used, then, irrespective of whether or notthe timer has reached the antenna stop time T1, in step S350, the fourthrelay switch SW4 is turned off to stop the rotation of the antenna 4.Then, the flow returns to step S340, where whether or not the door isopen is checked again. So long as the door is found to be open and inaddition the rotary stage 7 is found to be used, the operations in stepsS340, S341, and S350 are repeated. By contrast, if, in step S341, therotary stage 7 is found not to be used, then the flow proceeds to stepS360, where the fourth relay switch SW4 is turned on to rotate theantenna 4. Likewise, if, in step S340, the door is found not to be open,the flow proceeds to step S360, where the fourth relay switch SW4 isturned on to rotate the antenna 4.

Next, in step S370, whether or not the count of the stop timer hasreached the predetermined value T1 that was set in step S310 describedabove is checked. If the count is found to have reached thepredetermined value T1, then the flow proceeds to step S380, where thefourth relay switch SW4 is turned off so stop the rotation of theantenna 4, finishing the flow after heating. If the count is found notto have reached that value, the flow returns to step S330 to repeat theoperations in steps S330 to S370.

In the above description, the operations after the stopping of heatingare described as being performed after the course of heating. It is,however, also possible to perform the operations after the stopping ofheating in the same manner after temporary stopping of heating duringthe course of heating, for example temporary stopping of heatinginstructed with the press of a key or stopping of heating as a result ofthe door being opened. The control whereby the antenna is rotated duringheater heating may be performed also when high-frequency heating andheater heating are repeated alternately or are performed simultaneously.

As described above, with a high-frequency heating apparatus according tothe present invention, in a case where a rotary member is a rotary stageon which to place a heating target, while the advantages of aconventional antenna-type high-frequency heating apparatus aremaintained, it is possible to enhance the heating efficiency in grillheating and oven heating, and it is also possible to achieve uniformcooking by sophisticated controls.

On the other hand, in a case where the rotary member is a stirringmember placed in a container placed on a stage, while the advantage ofan antenna-type microwave oven that the floor of the heating compartmentis a flat surface without holes and is thus easy to clean, it ispossible to stir foodstuffs put in the container placed in the heatingcompartment.

INDUSTRIAL APPLICABILITY

High-frequency heating apparatuses according to the present inventionfind application not only in simple microwave ovens but also inmicrowave ovens equipped with composite heating functions so as to becapable of grill heating and oven heating.

1. A high-frequency heating apparatus comprising: a heating compartmentin which a heating target is heated; a high-frequency wave generatorthat generates a high-frequency wave; a waveguide through which thehigh-frequency wave generated by the high-frequency wave generator isguided to an opening formed in the heating compartment; a freelyrotatable antenna that feeds the high-frequency wave inside thewaveguide into the heating compartment through the opening and that hasa receiver portion and a radiator portion; a motor that rotates theantenna; and a stage that is provided above and close to the antenna soas to partition an interior of the heating compartment and that is madeof a dielectric material, wherein a rotary member is placed on thestage, either magnets are provided on both the rotary member and theantenna, or a magnet is provided on one of the rotary member and theantenna and a magnetic material is provided on the other, and a magneticcoupling between the antenna and the rotary member is exploited torotate the rotary member as the antenna is rotated.
 2. Thehigh-frequency heating apparatus of claim 1, wherein the rotary memberis a rotary stage including: a support member having a plurality ofrollers and magnets; and a table that is supported on the support memberand on which the heating target is placed.
 3. The high-frequency heatingapparatus of claim 2, wherein the table is supported on the plurality ofrollers by being kept in contact therewith so that, as the rollersrotate, the table rotates.
 4. The high-frequency heating apparatus ofclaim 2, wherein the support member is made of metal, and has at leasteither an opening or a cut through which to pass the high-frequency waveradiated from the antenna.
 5. The high-frequency heating apparatus ofclaim 1, wherein the rotary member is a stirring member provided in acontainer placed on the stage.
 6. The high-frequency heating apparatusof claim 5, wherein the stirring member includes: a disk-shaped base; astirring wheel that is formed on the base; and two or more rollerspivoted in a peripheral portion of the base.
 7. The high-frequencyheating apparatus of claim 1, wherein a restricting member is providedon at least one of the antenna and the stage in order to restrictmovement of the antenna in an axial direction.
 8. The high-frequencyheating apparatus of claim 7, wherein the antenna is composed of acylindrical receiver portion and a substantially disk-shaped radiatorportion fitted at a top end of the receiver portion coaxially therewith,and the restricting member is projections formed on a top surface of theradiator portion of the antenna at equal angular intervals in acircumferential direction.
 9. The high-frequency heating apparatus ofclaim 7, wherein the antenna is composed of a cylindrical receiverportion and a substantially disk-shaped radiator portion fitted at a topend of the receiver portion coaxially therewith, and the restrictingmember is rollers fitted on the radiator portion of the antenna at equalangular intervals in a circumferential direction.
 10. The high-frequencyheating apparatus of claim 1, wherein a first magnet is provided on theantenna, with a side of the first magnet facing the stage covered with anonmagnetic member and a side of the first magnet facing a floor of theheating compartment covered with a magnetic member, and a second magnetor a magnetic material is provided on the rotary member in a positioncorresponding to the first magnet.
 11. The high-frequency heatingapparatus of claim 10, wherein the antenna is formed of a nonmagneticmember, and the first magnet is provided on a bottom surface of theantenna, with a surface of the first magnet covered with a magneticmember.
 12. The high-frequency heating apparatus of claim 10, whereinthe antenna is formed of a magnetic member, and the first magnet isprovided on a top surface of the antenna, with a surface of the firstmagnet covered with a nonmagnetic member.
 13. The high-frequency heatingapparatus of claim 1, further comprising: a lower heater that isprovided close to a periphery of the antenna; and a controller forcontrolling operation of the motor and the lower heater, wherein, whenthe lower heater is heated, the antenna is rotated.
 14. Thehigh-frequency heating apparatus of claim 13, wherein, when the lowerheater stops being heated, the antenna is rotated under a predeterminedcondition.
 15. The high-frequency heating apparatus of claim 14, whereinthe predetermined condition is after the lower heater stops being heateduntil a timer provided for counting a time elapsed thereafter counts apredetermined length of time.
 16. The high-frequency heating apparatusof claim 14, wherein the predetermined condition is after the lowerheater stops being heated until a temperature sensor for sensingtemperature in the heating compartment falls to a predeterminedtemperature.
 17. The high-frequency heating apparatus of claim 13,wherein a detector for detecting whether a door of the heatingcompartment is open or closed is provided so that, when the door isdetected to be open after the lower heater stops being heated, rotationof the antenna is stopped.
 18. The high-frequency heating apparatus ofclaim 13, wherein, when the rotary member is not used, even if the dooris open after the lower heater stops being heated, rotation of theantenna is not stopped.
 19. The high-frequency heating apparatus ofclaim 14, wherein a detector for detecting whether a door of the heatingcompartment is open or closed is provided so that, when the door isdetected to be open after the lower heater stops being heated, rotationof the antenna is stopped.
 20. The high-frequency heating apparatus ofclaim 15, wherein a detector for detecting whether a door of the heatingcompartment is open or closed is provided so that, when the door isdetected to be open after the lower heater stops being heated, rotationof the antenna is stopped.
 21. The high-frequency heating apparatus ofclaim 16, wherein a detector for detecting whether a door of the heatingcompartment is open or closed is provided so that, when the door isdetected to be open after the lower heater stops being heated, rotationof the antenna is stopped.
 22. The high-frequency heating apparatus ofclaim 14, wherein, when the rotary member is not used, even if the dooris open after the lower heater stops being heated, rotation of theantenna is not stopped.
 23. The high-frequency heating apparatus ofclaim 15, wherein, when the rotary member is not used, even if the dooris open after the lower heater stops being heated, rotation of theantenna is not stopped.
 24. The high-frequency heating apparatus ofclaim 16, wherein, when the rotary member is not used, even if the dooris open after the lower heater stops being heated, rotation of theantenna is not stopped.
 25. The high-frequency heating apparatus ofclaim 17, wherein, when the rotary member is not used, even if the dooris open after the lower heater stops being heated, rotation of theantenna is not stopped.
 26. The high-frequency heating apparatus ofclaim 19, wherein, when the rotary member is not used, even if the dooris open after the lower heater stops being heated, rotation of theantenna is not stopped.
 27. The high-frequency heating apparatus ofclaim 20, wherein, when the rotary member is not used, even if the dooris open after the lower heater stops being heated, rotation of theantenna is not stopped.
 28. The high-frequency heating apparatus ofclaim 21, wherein, when the rotary member is not used, even if the dooris open after the lower heater stops being heated, rotation of theantenna is not stopped.
 29. The high-frequency heating apparatus ofclaim 3, wherein the support member is made of metal, and has at leasteither an opening or a cut through which to pass the high-frequency waveradiated from the antenna.